The faster handwriting-recognition results are returned, the better a user's experience will be. Conventional handwriting-recognition techniques typically have a fundamental bottleneck in detecting when the user finishes writing. This bottleneck often undesirably delays triggering the handwriting-recognition process.
Conventional ways for detecting that a user has finished writing and that handwriting recognition should be triggered typically include one or more of the following three techniques.
First, a timer is set upon detecting that the user has lifted the pen off the handwriting-recognition surface, which be referred to as a pen-up event. If a pen-down event, which occurs when a user places the pen on the handwriting-recognition surface, is not detected before the timer expires, it is inferred that the user has finished writing.
Second, if the user touches outside of a current handwriting-recognition-task area or inside a next task area, the pen-down event is interpreted as completion of the handwriting to be recognized from the current task area.
Third, if the user presses a soft key, labeled “End” or the like, the button-pressed event is interpreted as an indication from the user that the user is finished writing and that recognition should be triggered.
These three conventional techniques for determining when a user has stopped writing in a handwriting-recognition-task area have various shortcomings.
For the first technique, preferred timer values can vary from user to user depending on the users' writing speeds. Shorter timer values can cause a significant usability problem because, for a slow writer, timeouts may undesirably occur when the user hasn't finished writing yet. Some systems allow the user to set the value. The timer value usually is set to a value between 1 and 3 seconds. Since a user's writing speed can change dynamically, the fixed timer value may not work well under certain conditions. If the value is set to 3 seconds for example, the typical frustration of the handwriting recognition being triggered too early can be avoided, but the writing experience can be tedious because the user has to wait a relatively long time for recognition to be triggered.
With no automatic timers, the “End”-button approach does not present problems related to triggering recognition before or after recognition is desired. A shortcoming of the “End”-button approach, though, is that it reduces the quality of the user's experience by requiring many button presses. The repeated hand movement associated with these button presses gets tiresome, represents a significant overhead from the user's point of view, and disturbs the user's train of thought in composing sentences.
For the third technique discussed above, recognition is triggered for handwriting in a current task area when the user starts writing in a next task area. Although this technique works reasonably well, it does not take advantage of the time between when the user lifts the pen from the current task area and when the user puts the pen down in the next task area. Further, once the pen-down event has occurred, the user is typically already focused on writing in the next task area. The user may therefore ignore any recognition results provided for the handwriting entered in the previous task area. For any of the foregoing reasons, triggering handwriting recognition for a previous handwriting-recognition task area while the user moves the pen from the previous task area to a new task area would be desirable.